The basic objective of this project is to utilize a population of patients with cortical lesions to gather auditory data which will form the basis for refining our insight into psychoacoustic phenomena and for expanding the theory of central auditory behavior. The specific aims of the study are to investigate the effects of cortical damage on various types of dichotically presented auditory stimuli, with special emphasis on the degrading effects of cortical lesions on such signals. A corollary interest is the determination of whether or not auditory performance by such subjects can provide information relevant to the relative influence of the two hemispheres in the interpretation of auditory stimuli, and whether or not the location of the lesion has differential effects on the total capacity of the auditory system for receiving and interpreting information correctly. An auxiliary goal of these investigations is to determine the value of certain auditory tasks in delineating site and extent of cortical damage and in monitoring changes in auditory function over time in certain types of cortical lesions. An anticipated result of some of the experiments is the understanding of the effect of damage to auditory cortex on the patient's everyday reaction to the auditory world and how that reaction influences his successful rehabilitation. Since this study deals with living subjects, sites of lesion and the effects of such lesions on other aspects of the subjects' performance in a test situation must be determined. To that end, we have enlisted the assistance of neurological and aphasia specialists who will offer consultation and evaluation as needed. BIBLIOGRAPHIC REFERENCES: "Dichotic Perception of Simultaneous and Time-Staggered Synthetic Musical Chords," B. W. Friedrich and D. Noffsinger, 50th National Convention of the American Speech and Hearing Association, Washington, D. C., November, 1975. "Central Masking for Subjects with Lesions Involving the Auditory Temporal Cortex," H. B. Calder and Douglas Noffsinger, 91st Meeting of the Acoustical Society of America, Washinton, D. C., April, 1976.